Functions
6-1777SA6 Manual
C53000-G1176-C133-1
Figure 6-96 Example of adaptive dead time (ADT)
As is shown by the example, the adaptive dead time has the following advantages:
• The circuit-breaker at position II is not reclosed at all if the fault persists and is
therefor not unnecessarily stressed.
• With non-selective tripping by overreach at position III no further trip and reclose
cycles occur here because the short-circuit path via busbar B and position II
remains interrupted even in the event of several reclosure attempts.
• At position I overreach is allowed in the case of multiple reclosures and even in the
event of final tripping because the line remains open at position II and therefore no
actual overreach can occur at I.
The adaptive dead time also includes the reduced dead time because the criteria are
the same. There is no need to set the reduced dead time as well.
Close Command–
transfer
(Remote–CLOSE)
With close command transmission the dead times are only set at one line end. The
other (or the others in case of lines with more than two ends) is (are) set to “adaptive
dead time”. These ends respond to the received close command from the transmitting
end.
The transmission of the close command by the transmitting line end is delayed until it
is sure that the local reclosure was successful. This means that following reclosure
one further possible local fault detection is waited for. This delay prevents
unnecessary closing at the remote end on the one hand but also increases the time
until reclosure takes place there. This is not critical for a single-pole interruption or in
radial or meshed networks because no stability problems are expected under these
conditions.
The close command may be transferred by means of any signal transmission method.
Connecting an
External Reclosure
Device
If the 7SA6 has to work with an external reclosure device, the binary inputs and
outputs provided for this purpose must be taken into consideration. The following
inputs and outputs are recommended:
Binary inputs:
!(QDEOH$5]RQHV With this binary input the external reclosure device
controls stages of the individual short-circuit protection
functions which are active before reclosure (e.g.
overreaching zone in the distance protection). The input can
be omitted if no overreaching stage is required (e.g.
distance protection with comparison mode, see also above
under subtitle “Selectivity before Reclosure”).
!2QO\SK$5 The external reclosure device is only programmed for 1-
pole; the stages of the individual protection functions that
are activated before reclosure via F.No. only do so in
Z1B
A, B, C busbars
I, II, III relay locations
tripped circuit-breakers
Z1
Z1B
Z2
Z1
ABC
I
(defined dead times) II (ADT) III
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